Electrochemical detection is attractive because it provides high sensitivity, small dimensions, low cost, fast response, and compatibility with microfabrication technologies. These characteristics led to the development of a variety of sensors based on amperometric, potentiometric, and impedimetric signals, and the assembly of sensors into an array format for chemical, biochemical, and cellular applications. Typically, in such systems, analytes are distributed among an array of confinement regions or microwells (also referred to herein as “wells” or “reaction chambers”), and reagents are delivered to such regions by a fluidics system that directs the flow of reagents through a flow cell containing the sensor array.
Some applications involve the distribution of nucleic acid molecules attached to supports (e.g., particles or microbeads) in an array format. For example, several sequencing methods involve analysis of nucleic acid libraries, where individual members of the libraries are attached to particles that are distributed into an array of microwells. For such applications, increasing the number of microwells into which particles (or microbeads) are loaded can be desirable, because empty microwells may not provide useful information. The percentage of microwells that receive a particle or microbead can be referred to as the “loading efficiency.” Alternatively, in sequencing applications the loading efficiency can refer to the percentage of microwells in the array yielding a readable sequence. Poor loading efficiencies (e.g., loading efficiencies less than 50%) increase the overall cost and effort associated with a chemical/biological experiment.
Therefore, improved loading efficiencies in microwell arrays would be desirable.